Income Taxes (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Effective income tax
Effective tax rate (as a percent)	36.20%	34.60%	32.60%	37.10%
Annual estimate
Effective income tax
Effective tax rate (as a percent)			38.00%